Device and process for the production of oils or other extractable substances

ABSTRACT

A device for the production of oils by pressing and extracting a raw material containing oleiferous or extractable substances in the presence of a liquid or supercritical extraction agent. The device includes an inlet for said raw material, a substantially cylindrical pressing body having outlets for oils and being connected to said inlet, and a press screw movably provided in said cylindrical pressing body whereby said raw material is transported from said inlet into said pressing body and therefrom to a discharge outlet while being pressed. In addition, the pressing body is proof-sealed against its surroundings by a jacket and the press screw and/or the pressing body include outlets wherethrough a liquid extraction agent may be introduced into said raw material present in said pressing body. At the outlet of said pressing body, a pipe permitting degassing of the press cake discharged from the press by applying a vacuum, thus removing the solvent from it, may be provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is concerned with a device, namely a screw press, for theproduction of oils by pressing and extracting an oleiferous raw materialin the presence of a liquid extraction agent. The device includes aninlet for the raw material, a substantially cylindrical pressing bodyhaving outlets for oil and being connected to the inlet, and a pressscrew movably provided in the cylindrical pressing body. The press srewtransports the raw material from the inlet into the pressing body andtherefrom to a discharge outlet while pressing it.

For the purposes of the present specification and claims, the terms"oil" and "oleiferous" also refer to "fat" and "fatty" as well as to"extractable substances".

2. Description of Related Art

From DE-A-30 16 877, a process for the continuous separation of fat fromorganic raw materials is known wherein the raw materials are firstshredded and optionally dried, then mashed using a fat dissolving agentand thereafter fed to a screw press.

Also, GB-A-1 340 484 is concerned with pressing in the presence of anextraction agent.

DE-C 665 873 refers to a process according to which an extraction agentis fed during pressing.

According to the process known from GB-A-1 340 484, palm oil may beproduced by pressing the oleiferous fruit while adding a solvent to thematerial to be pressed under normal pressure at the intake of the press.

All known screw presses whereby oil is produced have the disadvantage inthat their oil yields are not satisfactory.

Thus it is the object of the present invention to provide a screw presswhereby the oleiferous raw material may be deoiled to an extent of96-98%, based on the total oil content, in one single operation step.

BRIEF SUMMARY OF THE INVENTION

The device according to the invention for the present production of oilby pressing and extracting an oleiferous raw material in the presence ofa liquid extraction agent, comprises an inlet for the raw material, asubstantially cylindrical pressing body having outlets for oil and beingconnected to the inlet, and a press screw movably provided in thecylindrical pressing body. The press screw transports the raw materialfrom the inlet into the pressing body and therefrom to a dischargeoutlet while pressing it wherein

said pressing body is pressure-sealed against its surroundings by meansof a jacket and

said press screw and/or said pressing body comprise outlets wherethrougha liquid extraction agent may be introduced under pressure into the rawmaterial present present invention consists essentially of the jacketcomprising at its lower.

A convenient embodiment of the device according to the present inventionconsists essentially of the jacket comprising at its lower portion a tubfor collecting the oil/extraction agent mixture being discharged fromthe pressing body.

The tub is suitably provided with an outlet for the oil/extraction agentmixture, said outlet having a gasproof connection to a pressure vessel.

The invention is also concerned with a process for the production ofoils and/or extractable substances by pressing and extracting oleiferousand/or extractable substances-containing raw material in the presence ofa liquid and/or a supercritical extraction agent, an oil or extractedsubstance/extraction agent mixture being obtained wherefrom theextraction agent is removed, wherein the raw material is shredded andpressed using the above-described device according to the inventionwhile the extraction agent is simultaneously introduced under pressureinto the raw material.

Using the device according to the invention, carbon dioxide in liquefiedstate and/or supercritical state and/or hydrocarbons in liquid and/orsupercritical state are particularly useful as the liquid extractionagent.

It has proven advantageous to treat the shredded raw material with anoil-dissolving liquid prior to pressing. Thus the oil layer surroundingthe shredded raw material particles is removed, whereby friction betweenthe particles during pressing is increased and a very good build-up ofpressure in the pressing body as well as a very good sealing of thepressing body towards its upstream end are achieved.

Further, the device according to the invention is appropriate forcarrying out transesterification processes. Thus for instance it ispossible to transesterify triglycerides contained in the oleiferous rawmaterial with an alcohol, thus producing fatty acid alkyl ester.Therefore the invention is also concerned with the use of the deviceaccording to the invention for the production of fatty acid esters bytransesterification of a triglyceride contained in the oleiferous rawmaterial with an alcohol in the presence of a catalyst, said use beingcharacterized in that

said triglyceride-containing raw material is shredded,

the shredded raw material is introduced into a pressing body,

alcohol and a catalyst are introduced into the raw material through theoutlets provided in the press screw and/or in the pressing body undersuch conditions that the triglyceride contained in the raw material istransesterified with the alcohol, thus fatty acid ester being producedwhich is discharged from the pressing body through the outlets,whereafter

the fatty acid ester is purified in a known manner.

Transesterification means the reaction of triglycerides, i.e. vegetableand animal fats and oils, with alcohols such as methanol, ethanol,butanol and isopropanol, particularly methanol and ethanol, thusproducing the monoesters of fatty acids and glycerine. Fatty acid methylesters are of increasing importance as a substitute for diesel fuel.

From AT-B 394 374, a transesterification process is known. According tothis process, an excess of 1.10 to 1.80 mol of the alcohol employed permol of fatty acid transesterified with glycerine is used. From AT-B 388743 a process for the production of a fatty acid mixture of waste fatsor oils and the use of this mixture as fuel is known.

Also AT-B 397 966 describes the production of fatty acid esters of lowmonovalent alcohols by transesterification of, e.g., rapeseed oil.According to this process, transesterification is carried out in thepresence of a solid basic catalyst at a catalyst excess of not more than1.6 mol per mol of fatty acid bound as glyceride.

From AT-B 397 510 a two or multi-step transesterification process isknown.

As the catalysts for transesterification, usually basic catalysts suchals alkali hydroxides, metal hydrides, alcoholates, carbonates oracetates and acid catalysts such as mineral acids are used. Thecatalysts most frequently used are sodium and potassium hydroxide aswell as sodium methylate which dissolved in alcohol are added e.g. to avegetable oil. Such a process is known from AT-B 386 222.

The known transesterification starts with a diphase system oftriglyceride and alcohol containing the catalyst. While the reactionproceeds and ester is produced, a homogeneous phase forms which againturns biphase when glycerine is produced and discharged (raw ester phaseand glycerine phase).

The use according to the invention of the transesterification deviceaccording to the invention is based on the finding that, among otherreasons, transesterification may be advantageously carried out in theoleiferous raw material itself, i.e. that it is not necessary to firstproduce the oil to be transesterified from the raw material and thentransesterify it. Thus transesterification and separation of the fattyacid alkyl ester may be carried out in one single step.

It is evident to those skilled in the art that when the pressing deviceis used according to the invention, first a biphase mixture consistingsubstantially of ester and glycerine will be obtained and the productionof pure ester from this biphase mixture is possible using knowntechniques.

A preferred use of the press according to the invention is characterizedin that when starting, pressing an agent which binds the residualhumidity of the oil or fat-containing substance is introduced into theoleiferous substance, thus preventing an increased saponification afteradding the catalyst.

Conveniently, pressing is carried out while cooling.

By means of the attached drawing, the invention is illustrated in moredetail.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1 shows a section through a screw press of the prior art; and

FIGS. 2 and 3 show advantageous embodiments of the screw press accordingto the invention; and FIG. 4 shows the pressure course along thepressing body of the screw press according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 schematically shows a section through a known screw press (madeby the company Krupp). Reference number 1 refers to a cylindricalpressing body connected to an inlet 2 for the raw material 3 to bepressed and extracted. The raw material 3 is seized by spirals 11,pressed into cylindrical pressing body 1, and transported through. Oilis pressed from the raw material which flows downwards through outletsusually including straining rods (not shown) and is discharged frompressing body 1. The oil being discharged from pressing body 1 isindicated by means of drops 4. The oil is collected in a tub (notshown).

After being transported through pressing body 1, the raw materialpressed is discharged by discharge outlet 6 provided in a component lajoined to the cylindrical pressing body 1.

In the embodiment shown, press screw 5 has three frustoconical taperings12 whereat the material to be pressed is subjected to an increasedpressure. After overcoming such a tapering, the pressure naturally willdrop somewhat again. Such a change of pressure favors pressing, andsolvent injected at this point will diffuse down to the level of thecell wall due to this short-time drop in pressure.

FIG. 2 shows a section through an embodiment of a screw press accordingto the invention which can be easily obtained by adapting the knownscrew press shown in FIG. 1. Additionally, the screw press according tothe invention shown comprises a jacket 7, 7a which proof-seals pressingbody 1 in the portion of those outlets (not shown) wherefrom oil 4 isdischarged into tub 7a, which in the present case is identical with thelower portion of jacket 7, against its surroundings.

Press screw 5 is hollow and comprises outlets 8 wherethrough a liquidextraction agent may be introduced under pressure into the raw materialpresent in pressing body 1. The extraction agent is fed under pressureto the hollow press screw 5 through feeding 13. It has been shown thatpressing of the raw material carried out in this way whilesimultaneously feeding an extraction agent under pressure gives a veryhigh oil yield of at least 96%, based on the total oil content. Due tothe high pressures in the material to be pressed, the solvent injectedenters a supercritical state, and the solubility of the oil or theextractable substances increases in the solvent.

Reference number 4a indicates the mixture of oil and extraction agentdischarged out of the pressing body 1 in the area of the straining rods(not shown) which is collected in tub 7a, in the present embodimentformed by the lower portion of jacket 7, and enters a receptacle (notshown) through gasproof outlet 10. The oil or the extractable substancemay be produced in a known manner by removing the extraction agent fromthe mixture oil or extractable substance/extraction agent.

When a hydrocarbon which under normal conditions is liquid is used as anextraction agent, it may be separated by distillation.

When a hydrocarbon which under normal conditions is gaseous or CO₂ isused as an extraction agent, it is conducted under pressure andtherefore in liquid or supercritical state from the press into apressure vessel. Therefrom it may be reconducted from the liquid to thepress again in liquid or supercritical state by evaporation or suctionand subsequent pressure increase and temperature reduction whilepressure is lowered (regeneration and recirculation).

Moreover, it has been shown that in the device according to theinvention liquid carbon dioxide is very useful as an extraction agent.It is evident to those skilled in the art that in this case suchpressure/temperature conditions must be applied whereunder carbondioxide is present in liquid state or in supercritical state. Thisapplies to feeding 13 and in hollow press screw 5 as well as duringpressing of the raw material, i.e. within pressing body 1, within tub7a, within outlet 10 and within the subsequent receptacle, which in thiscase must be provided as a pressure vessel. By setting such pressure andtemperature conditions, a liquid mixture of oil or extractablesubstances and carbon dioxide is present in tub 7a. Carbon dioxide maybe removed from the mixture by evaporation by means of a simple pressurereduction.

FIG. 3 shows another preferred embodiment of the device according to theinvention wherein the extraction agent, i.e. liquid hydrocarbon orliquid carbon dioxide, is not introduced by means of press screw 5 butby means of pressing body 1 into the raw material which has just beenprocessed. These outlets are referred to by reference number 9. Theextraction agent is fed to outlets 9 by means of feedings 14.

Conveniently, outlets 9 are each provided immediately after a tapering12 of press screw 5. This improves the production of oil to asignificant degree.

Shortly before the material to be pressed is discharged from the press,a flush nozzle (not shown) may be provided wherethrough acids and/oroil-displacing and/or oil-soluble substances may be additionallyinjected.

FIG. 4 shows the pressure course in pressing body 1, the X-axisindicating the length of the cylindrical pressing body and the ordinateindicating the pressure. From FIG. 4 it can be seen that the pressureincreases when screw 5 seizes the material to be pressed and transportsit into pressing body 1. For a good build-up of pressure it is importantthat the oil layer is superficially removed from the shredded rawmaterial by washing it with extraction agent. In FIG. 4, exemplarypressures are indicated.

First, pressure in pressing body 1 continuously rises until the firsttapering 12 is overcome, whereafter pressure drops sharply to afterwardsrise again continuously until the next tapering 12. By this pressurechange, the oil production is improved, i.e. the particles to be pressedare reoriented.

In the following, a preferred embodiment of the process according to theinvention for the production of oil will be described in more detail.

Before processing, non-oleiferous deads are removed from the rawmaterial and the raw material is decorticated (depeeled). Then it isdried to a water content of about 2-5%.

After drying, the oleiferous raw material is shredded to a particle sizeof 0.5-2 mm. Thereafter it is washed with an oil-dissolving liquid suchas hexane and/or an acid. The humid raw material thus prepared can befed to the press.

By completely separating the peel from the raw material, it is possibleto increase the pressing capacity up to 40% compared to the knownprocesses. Moreover, due to this separation the protein content of thepress cake is increased by the portion of the removed peel.

(When the press cake is discharged from the press, the extraction agentcontent is from 4-8%. This is significantly less than in the processesknown today.

At discharge outlet 6, the device according to the invention permits thedischarged material to be pressed to be conducted in warm state into apipe (not shown) provided with suction outlets so as to recover thesolvent discharged after reducing pressure by means of suction andcondensation. Due to this possibility, the energy demand for removingthe residual solvent is significantly lowered, since the heat of thematerial to be pressed is used for evaporating the solvent.

As already mentioned above, the device according to the invention mayalso be used to catalytically transesterify triglycerides in the rawmaterial during pressing. For that purpose, a mixture of alcohol andcatalyst is introduced into the raw material instead of the extractionagent through outlets 8 and 9 respectively. In this case, liquid 4 and4a respectively which is discharged from pressing body 1 is a mixture ofester, glycerine, alcohol and catalyst, wherefrom ester may be producedin a known manner.

For transesterification, the shredded raw material should not containmore than 0.5% of water. Conveniently, the raw material to be processedis contacted already prior to pressing with the alcohol/catalyst mixturefor 20-30 minutes.

The use according to the invention of the screw press according to theinvention allows transesterification degrees exceeding 99% to beachieved.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

I claim:
 1. A device for the production of oils or other extractablesubstances by pressing and extracting a raw material of plant origincontaining oleiferous or extractable substances in the presence of aliquid extraction agent, said device comprising:an inlet for said rawmaterial; a pressing body wherein a movable press screw is provided;means for introducing said extraction agent into said pressing body; adischarge outlet for said raw material pressed;said movable press screwis a single press screw arranged in said pressing body for transportingsaid raw material from said inlet into said pressing body and therefromto said discharge outlet while pressing said raw material undersimultaneous introduction of said extraction agent into said rawmaterial subjected to pressing; and said pressing body is proof-sealedagainst its surroundings by means of a jacket.
 2. The device accordingto claim 1, wherein said means for introducing said extraction agentinto said pressing body are outlets provided in said press screw,wherethrough a liquid extraction agent may be introduced under pressureinto said raw material present in said pressing body.
 3. The deviceaccording to claim 1 or 2, wherein said jacket comprises a tub forcollecting the oil/extraction agent mixture discharged from saidpressing body.
 4. The device according to claim 1 or 2, furthercomprising a tub for collecting the oil/extraction agent mixturedischarged from said pressing body and wherein said tub is provided withan outlet for said oil/extraction agent mixture, said outlet beingconnected to a pressure vessel through a gasproof and pressure-proofconnection.
 5. A process for the production of oils by pressing andextracting a raw material of plant origin containing oleiferous orextractable substances in the presence of a liquid extraction agent,wherein an oil or extractable substances/extraction agent mixture isobtained wherefrom said extraction agent is removed, comprising thesteps of:shredding and pressing said raw material using a deviceaccording to claim 1 or 2 and simultaneously introducing said extractionagent under pressure into said raw material subjected to pressing. 6.The process according to claim 5, further comprising the step ofemploying carbon dioxide in liquefied state and/or in supercriticalstate or a hydrocarbon in liquid or supercritical state as said liquidextraction agent.
 7. The process according to claim 5, furthercomprising the step of treating said shredded raw material with anoil-dissolving liquid prior to pressing.
 8. A process for the productionof fatty acid esters using the device according to claim 1 or 2 bytransesterification of a triglyceride contained in said oleiferous rawmaterial of plant origin with an alcohol in the presence of a catalyst,comprising the steps of:shredding said triglyceride-containing rawmaterial; introducing said shredded raw material into said pressingbody; introducing the alcohol and the catalyst through outlets providedin at least one of said press screw and said pressing body into said rawmaterial under such conditions that said triglyceride contained in saidraw material is transesterified with said alcohol, fatty acid esterbeing produced which is discharged from said pressing body through saidoutlets; and purifying said fatty acid ester.
 9. The device according toclaim 1, wherein said means for introducing said extraction agent intosaid pressing body are outlets provided in said pressing body,wherethrough a liquid extraction agent may be introduced under pressureinto said raw material present in said pressing body.